High Energy Theory Seminar

I define and study TQFTs which generalize the Dijkgraaf-Witten TQFT and can be described on a lattice using discrete 1-form and 2-form gauge fields. The gauge group is replaced by a gauge 2-group. It is proposed that 2-group TQFTs classify gapped phases of gauge theories as well as Symmetry Protected Topological phases of matter. They can also be used to define discrete theta-parameters on the lattice.